HLA-G expression in placenta in relation to HLA-G genotype and polymorphisms

Problem: The expression of the non-classical human leukocyte antigen (HLA) class Ib gene, HLA-G, seems to be important at the feto-maternal interface. The HLA-G molecule is almost monomorphic and expressed in both membrane-bound and soluble isoforms. It has been shown to inhibit natural killer cell -mediated lysis and influence cytokine expression. HLA-G gene polymorphism has been linked to differences in gene expression profile of alternatively spliced HLA-G transcripts and levels of specific HLA-G messenger RNA (mRNA) isoforms. Furthermore, aberrant HLA-G expression has been reported in preeclamptic placentas. On this background it is of general interest to further elucidate any associations between HLA-G polymorphism and protein expression. Methods: We have investigated HLA-G protein expression by immunohistochemistry in HLA-G genotyped placentas from term. HLA-G mRNA expression in preeclamptic placentas and in control placentas was also studied by microarray technology. Results and conclusions: The studies of HLA-G protein expression in term placentas by immunohistochemical analysis showed no clear associations with HLA-G genotypes although this could be because of the very semi-quantitative nature of this technique. However, we found a tendency towards reduction of HLA-G mRNA expression in placentas from preeclamptic cases compared to matched controls with the use of microarray technology.